THE US has been warned of potentially "devastating consequences" if it blocks China from islands it has built in contested waters in the South China Sea, according to Chinese media reports.

And in more inflammatory comments, prospective US Secretary of State Rex Tillerson was told he better watch his mouth, after the former ExxonMobil CEO told US senators that he would seek to deny Beijing access to the artificial islands.

China's actions in the region are comparable to Russia's invasion of Crimea, he said, a comment that did not sit well with the nuclear-armed Asian giant.

If Tillerson acted on his threats, Chinese state-owned China Daily warned "it would set a course for devastating confrontation between China and the US." Satellite photos show China has been hard at work building military facilities in the contested waters, which are also claimed by the Philippines and Vietnam, among others.

The sentiment former Australian Prime Minister Paul Keating to comment that Canberra needed to tell the incoming Trump administration from the get-go that Australia will sit out any US "adventurism" over South China Sea tensions.

"When the US secretary of state-designate threatens to involve Australia in war with China, the Australian people need to take note," he said in a statement.

Former Prime Minister Paul Keating wants Canberra to tell Trump that we’ll sit out any adventurism over South China Sea tensions.Stuart McEvoy for The Australian.

Australia should not provide naval commitment to joint operations in the South China Sea and no enhanced US military facilitation of such operations, he said.

Tillerson's claim China's control of access to the South China Sea would be a threat to the "entire global economy" was "ludicrous", Mr Keating said.

"No country would be more badly affected than China if it moved to impede navigation.

"On the other hand, Australia's prosperity and the security of the world would be devastated by war."

Under US President Barack Obama, Washington has claimed Beijing's activities in the region threaten freedom of navigation and overflight through the commercially and strategically vital waters.

But is has not taken a position on the ownership of the islets, reefs and shoals that sit in one of the world's hot spots.

Tillerson, however, explicitly said that the territories "are not rightfully China's."

"Unless Washington plans to wage a large-scale war in the South China Sea, any other approaches to prevent

Chinese access to the islands will be foolish," the nationalistic Global Times wrote in an editorial.

The paper, which is thought to have some insight into the thinking of more hawkish members of Chinese Communist Party, added that Tillerson better "bone up on nuclear power strategies if he wants to force a big nuclear power to withdraw from its own territories."

It has previously called on Beijing to increase its nuclear arsenal after Donald Trump threatened to up-end decades of US policy on Taiwan by suggesting he could recognise the island, which China regards as an indisputable part of its sovereign territory.

China's official reaction to the comments was muted, with foreign ministry spokesman Lu Kang politely urging Washington to mind its own business.

"The South China Sea situation has cooled down and we hope non-regional countries can respect the consensus that it is in the fundamental interest of the whole world," he said.